The present invention relates to engine controls and diagnostics, and more particularly to methods and apparatus for estimating gas temperatures of a vehicle engine, and even more particularly to methods and apparatus for estimating gas temperatures within a vehicle engine.
Internal combustion engine control strategies are generally known for precisely controlling engine intake air and injected fuel to balance the goals of low emissions, high fuel economy, and high engine performance. Efforts have been made to estimate the mass flow rate of air into an engine cylinder during a cylinder intake event. With an estimate of the mass flow rate of air into an engine cylinder during a cylinder intake event, an appropriate mass of relatively controllable fuel may be appropriately combined according to an engine control strategy. For example, a stoichiometric air/fuel ratio within the engine cylinder can be provided during a cylinder combustion event that supports efficient catalytic treatment of cylinder combustion products.
The mass of air flowing into an engine cylinder is dependent on air density and therefore dependent on air temperature. Recirculated engine exhaust (EGR) gas mass flow information is preferable for control of engine fueling and for high performance engine emissions control. In addition, EGR mass flow is dependent on EGR gas temperature, and accurate information of the temperature of air entering a cylinder is also desirable.
Direct sampling of air temperature has been proposed to provide air temperature information with the desired accuracy. However, conventional temperature transducer durability is relatively low in the inner environment of the cylinder intake. Furthermore, temperature transducers, such as thermocouples, typically lack the transient response characteristics desired to represent the temperature of the turbulent air mass passing through the intake runner to the cylinder during a transient. Therefore, indirect techniques are utilized for determining temperatures within an engine, including estimation techniques, and continuing improvement of the apparatus and methods for estimating temperatures within a vehicle engine are sought to provide the desired accuracy to balance engine-operating parameters such as low emissions, high fuel economy, and high engine performance.
In view of the foregoing, it should be appreciated that it would be desirable to provide methods and apparatus for estimating gas temperatures within a vehicle engine. Furthermore, additional desirable features will become apparent to one skilled in the art from the foregoing background of the invention and following detailed description of a preferred exemplary embodiment and appended claims.
In accordance with the teachings of the present invention, an apparatus is provided for estimating a plurality of gas temperatures in an engine of a vehicle. The apparatus comprises an exhaust temperature estimator configured to receive a velocity of the vehicle and an air mass flow rate. The exhaust temperature estimator is configured to estimate an exhaust gas temperature based at least upon the velocity of the vehicle and the air mass flow rate. The apparatus also comprises a first recirculated engine exhaust gas (EGR) temperature estimator coupled to the exhaust temperature estimator. The first EGR temperature estimator is configured to receive the exhaust gas temperature from the exhaust temperature estimator and further configured to receive an EGR mass flow rate. The first EGR temperature estimator is configured to estimate an EGR gas temperature at an EGR valve of the engine based at least upon the exhaust gas temperature and the EGR mass flow rate. Similarly, the apparatus comprises a second EGR temperature estimator coupled to the exhaust temperature estimator. The second EGR temperature estimator is configured to receive the exhaust gas temperature from the exhaust temperature estimator and further configured to receive the EGR mass flow rate. The second EGR temperature estimator is configured to estimate an EGR gas temperature at a throttle body of the engine based at least upon the exhaust gas temperature and the EGR mass flow rate. Furthermore, the apparatus comprises a charge temperature estimator coupled to the second EGR temperature estimator. The charge temperature estimator is configured to receive the EGR gas temperature at the throttle body from the second EGR temperature estimator. The charge temperature estimator is further configured to receive the velocity of the vehicle and the EGR mass flow rate. The charge temperature estimator is configured to estimate a charge gas temperature based at least upon the EGR gas temperature at the throttle body, the velocity of the vehicle, and the EGR mass flow rate.
In accordance with the teachings of the present invention, a method is provided for estimating a plurality of gas temperatures of a vehicle engine. The method comprises receiving a velocity of the vehicle and an air mass flow rate and estimating an exhaust gas temperature based at least upon the velocity of the vehicle and the air mass flow rate. The method also comprises receiving an EGR mass flow rate and estimating an EGR gas temperature at an EGR valve based at least upon the exhaust gas temperature and the EGR mass flow rate. In addition, the method comprises estimating an EGR gas temperature at a throttle body based at least upon the exhaust gas temperature and the EGR mass flow rate. Furthermore, the method comprises estimating a charge temperature based at least upon the EGR gas temperature at the throttle body, the velocity of the vehicle, and the EGR mass flow rate.